Speaking at a Capitol news conference with other Democrats, Pryor noted that women in Arkansas earn 77 cents for every dollar earned by men — leaving them with $9,300 less on average to support their families.

“My daughter is in college now. I want her to know that when she begins her career she’ll receive equal pay for equal work,” he said. “That’s why I was proud to support the Lilly Ledbetter Fair Pay Act. And it’s why I’m a proud co-sponsor of the Paycheck Fairness Act.”

Pryor’s daughter, Porter, is a freshman at the University of Arkansas at Fayetteville.

The Senate plans to take up the Paycheck Fairness Act on Wednesday. Although it has 55 co-sponsors including Pryor, it will likely fail to clear a procedural hurdle where a 60-vote margin is needed.

Democrats have introduced similar legislation for more than a decade without success. In 2012, Republicans defeated the effort on a similar procedural vote. Pryor has voted in favor of the bill in the past but has not been a co-sponsor.

Sen. Barbara Mikulski, D-Md., introduced the latest bill on Jan. 23, 2013. Pryor signed on as a co-sponsor on March 25, 2014, one of the last Democrats to do so.

Since signing on as a co-sponsor, Pryor’s Senate campaign has aggressively gone after his Republican rival Rep. Tom Cotton, R-Dardanelle, for opposing the legislation.

The campaign launched an online ad campaign March 28, saying the 30-second ad would run in heavy rotation statewide for several weeks.

“On the issues that really matter to women and families in Arkansas, issues like paycheck fairness for women in the workplace, Congressman Cotton just isn’t listening to us,” Amy Schlesing, a spokeswoman for Pryor’s campaign, said in a statement announcing the ad.

Last year, House Democrats attempted to bring the bill up for debate but were denied on a procedural vote, 226-192. Cotton voted against considering the measure.

Michael Teague, communications director for Pryor, said his sponsorship of the bill was unrelated to the campaign. When legislation is nearing a floor vote, it is not atypical for the author of a bill to seek additional co-sponsors, he said.

“He has supported the bill for half a decade and was asked to co-sponsor it and so he did,” Teague said.

Caroline Rabbitt, a spokeswoman for Cotton, said he opposes the bill but supports equal pay for equal work as is already required by law.

“The Equal Pay Act of 1963 already makes it illegal to discriminate based on gender. And while we all recognize workplace discrimination unfortunately still exists, it can’t be fixed through executive orders and new mandates that will only line the pockets of trial lawyers and harm merit pay,” she said.

Republicans also argue that the bill would hurt all workers by imposing tighter regulations on how employers compensate employees, making it nearly impossible for them to consider work quality, productivity and experience in awarding merit pay.

The Obama administration issued a statement strongly supporting the legislation saying it would enhance enforcement of equal pay laws by allowing workers to discuss pay with other employees without fear of retaliation.